Field of the Invention
The present invention relates to an automatic transmission for a vehicle, and more particularly, to a planetary gear train of an automatic transmission for a vehicle, which is capable of improving fuel efficiency by implementing an automatic transmission with multiple stages and implementing eight forward speeds using a minimum number of configurations, and capable of improving constant-speed driving performance of the vehicle by ensuring an operating point within a low RPM region.
Description of Related Art
The recent increase in oil prices has pushed carmakers into unlimited competition for enhancing fuel efficiency.
Accordingly, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted for simultaneously securing operability and fuel efficiency competitiveness by implementing an automatic transmission with multiple speed stages.
However, in the case of the automatic transmission, the number of internal components is increased as the number of gear shift stages is increased, and as a result, the automatic transmission may be difficult to mount, the manufacturing cost and weight may be increased, and power transmission efficiency may be deteriorated.
Therefore, in order to increase an effect of improving fuel efficiency by implementing an automatic transmission with multiple speed stages, it is important to develop a planetary gear train capable of maximizing efficiency using a small number of components.
In this respect, recently, an eight-speed automatic transmission has been applied to an actual vehicle, and researches and developments are being actively conducted on a planetary gear train that may implement gear shift stages for eight or more speeds.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.